Neoprene is 100% waterproof.
If it doesn't have holes, water won't "soak through" the fabric of a neoprene wetsuit. It can seep in through the zipper, and it can seep in from the neck, ankles, and wrists. I have a semi-dry wetsuit, and I'm amazed how dry I am when I take it off, and it doesn't even have a totally waterproof zipper. I still have my first SCUBA drtsyut. It is neoprene. It has attached booties and a neck seal and wrist seals and is just as waterproof as a paddling drysuit. Maybe more. They do make some tropical drysuits out of breathable material, but they aren't tough enough for cold water diving. My second SCUBA drysuit was crushed neoprene. Also totally waterproof, but doesn't suffer from losing insulating value at depth because it's already crushed. My current diving suit is a trilaminate suit with butyl (synthetic rubber) sandwiched between polyester layers, and i'ts awesome. Neoprene, like butyl, is synthetic rubber. Totally waterproof unless punctured.
Muck boots won't "soak through," but if you put your foot too far in the river, just like an open canoe, there's a hole in the top through which water may enter. The one thing I don't like about my Boggs is they have grab handles below the cuff, so they can't go as deep.
You already know that if you do develop a leak, you can fix it with aquaseal.